bit_floor.hpp

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// SPDX-License-Identifier: BSL-1.0
// SPDX-FileCopyrightText: Copyright (C) 2019 Tobias Hienzsch
 
#ifndef TETL_BIT_BIT_FLOOR_HPP
#define TETL_BIT_BIT_FLOOR_HPP
 
#include <etl/_bit/bit_width.hpp>
#include <etl/_concepts/builtin_unsigned_integer.hpp>
#include <etl/_limits/numeric_limits.hpp>
 
namespace etl {
 
/// \brief If x is not zero, calculates the largest integral power of two that
/// is not greater than x. If x is zero, returns zero.
///
/// \details This overload only participates in overload resolution if UInt is an
/// unsigned integer type (that is, unsigned char, unsigned short, unsigned int,
/// unsigned long, unsigned long long, or an extended unsigned integer type).
///
/// \returns Zero if x is zero; otherwise, the largest integral power of two
/// that is not greater than x.
///
/// \ingroup bit
template <etl::builtin_unsigned_integer UInt>
[[nodiscard]] constexpr auto bit_floor(UInt x) noexcept -> UInt
{
    if (x != 0) {
        return UInt(1) << static_cast<UInt>(static_cast<UInt>(etl::bit_width(x)) - UInt(1));
    }
    return 0;
}
} // namespace etl
 
#endif // TETL_BIT_BIT_FLOOR_HPP